Embil Villagra, Carmen, Farren, Gerrit, Fabbian, Giulio  ORCID: https://orcid.org/0000-0002-3255-4695, Bolliet, Boris, Abril-Cabezas, Irene, Alonso, David, Challinor, Anthony, Dunkley, Jo, Kim, Joshua, MacCrann, Niall, McCarthy, Fiona, Moodley, Kavilan, Qu, Frank Jia, Sherwin, Blake, Sifón, Cristóbal, van Engelen, Alexander and Wollack, Edward J.
2025.
The Atacama Cosmology Telescope: high-redshift measurement of structure growth from the cross-correlation of Quaia quasars and CMB lensing from ACT DR6 and Planck PR4.
Journal of Cosmology and Astroparticle Physics
2025
(12)
, 033.
10.1088/1475-7516/2025/12/033
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Abstract
We measure the amplitude of matter fluctuations over a wide range of redshifts by combining CMB lensing observations from ACT DR6 and Planck PR4 with the overdensity of quasars from Quaia, a Gaia and unWISE quasar catalog. Our analysis includes the CMB lensing power spectrum from ACT DR6, the auto-correlation of two Quaia quasar samples centered at z ≃ 1.0 and z ≃ 2.1, and their cross-correlations with CMB lensing from both ACT DR6 and Planck PR4. By performing a series of contamination and systematic null tests, we find no evidence for contamination in the lensing maps, contrary to what was suggested in previous Quaia cross-correlation analyses using Planck PR4 CMB lensing data. From the joint analysis of the quasar auto- and cross-correlations with CMB lensing, and including BOSS BAO data to break the degeneracy between Ωm and σ8, we obtain σ8 = 0.802+0.045-0.057, consistent with ΛCDM predictions from Planck primary CMB measurements. We also find consistent results using DESI BAO data. Combining the CMB lensing auto-spectrum with the cross-correlation measurement improves the constraint on σ8 by 12% relative to the lensing auto-spectrum alone, yielding σ8 = 0.804 ± 0.013. This dataset combination also enables a reconstruction of structure growth across redshifts. We infer a 12% constraint on the amplitude of matter fluctuations at z > 3, with a measurement at the median redshift of the signal of σ8(tilde z = 5.1) = 0.146+0.021-0.014, consistent with Planck at the 1.4σ level. These results provide one of the highest redshift constraints on the growth of structure to date.
| Item Type: | Article |
|---|---|
| Date Type: | Publication |
| Status: | Published |
| Schools: | Schools > Physics and Astronomy |
| Publisher: | IOP Publishing |
| ISSN: | 1475-7516 |
| Date of First Compliant Deposit: | 7 January 2026 |
| Date of Acceptance: | 14 October 2025 |
| Last Modified: | 07 Jan 2026 15:13 |
| URI: | https://orca.cardiff.ac.uk/id/eprint/183688 |
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